Dietary fiber and the role of fiber in the human diet and metabolism have been areas of extensive research recently, at least in part because numerous human diseases and disorders have been shown to benefit in some fashion from increased fiber content. It has been observed that persons whose diets are high in fiber-containing foods generally have a lower occurrence of intestinal disorders, cardiovascular diseases, and cancer, especially colon cancer.
Total dietary fiber (TDF) may be defined as plant material and other polymers in foods that upon ingestion are resistent to digestion, e.g., hydrolysis, by human gastrointestinal secretions and enzymes in the digestive system. Included within TDF are cellulose, hemicelluloses, lignin, lignin-containing material, pectic substances, and gums, as well as various other complex carbohydrates, i.e., polysaccharides. These compounds are largely found in the cell walls of plant tissues; however, some are found in the intracellular cement and seeds. The broad definition of TDF also includes nonplant materials like xylans and polydextrose. The following discussion, however, is limited to plant material.
Total dietary fiber is made of individual sugars and sugar acids that allow for binding, bonding, or reaction among themselves or with other compounds. TDF components may be generally classified as either soluble or insoluble. For example, cellulose and lignin are considered relatively insoluble, pectin and gums are highly soluble, and hemicelluloses exhibit a wide range of solubilities.
Increased intakes of TDF are correlated with a reduced incidence of major diseases such as cancer of the colon, hypercholesterolemia, atherosclerosis, diabetes, diverticulosis, constipation, hypertension, obesity, and gallstones. The different fiber components of TDF have different physiological functions and effects, both in degree and in kind. For example, it is generally believed that the level of serum cholesterol, and insulin dependency for diabetics, is reduced more by soluble fiber components; whereas, insoluble fiber components are considered effective in treating digestive disorders such as diverticulosis.
It is believed that the different physiological functions and effects of fibers is due, at least in part, to their properties of water-binding and absorption of organic molecules. The reduction in the incidence of cardiovascular diseases apparently relates to the ability of fiber to absorb materials such as bile acids and cholesterol. The intestinal related diseases appear to be affected by the water-binding properties of fiber and the decrease in the transit time of foods through the digestive system. Furthermore, the water-binding properties of fibers are believed to remove possible carcinogenic chemical factors by frequent elimination.
At least in part because of the different health benefits of soluble and insoluble fibers, a dietary fiber material with a relatively high total dietary fiber content that includes a combination of insoluble and soluble fiber components is sometimes advantageous. However, certain dietary fiber materials with a combination of soluble and insoluble fiber components have relatively low concentrations of soluble fiber. For obtaining the benefits associated with both soluble and insoluble fibers, a material that is relatively high in total dietary fiber and relatively high in soluble fiber content is desired. The presence of too high a concentration of soluble fiber, however, can present problems for food producers in the incorporation of the material into food products. This is partially due to a tendency for soluble fiber components to cause gelation, generally because of the high viscosity of these components. Thus, a material with a relatively high total dietary fiber content, i.e., combined soluble and insoluble components, and with a relatively high amount of soluble fiber components is desired provided the soluble fiber content is not so high as to present processing difficulties. An advantageous amount of soluble fiber is one that is high enough to provide health benefits, but not so high as to adversely affect the functional properties of the dietary fiber material and products into which it is incorporated.
There are some known dietary fiber materials that have advantageous amounts of total dietary fiber and soluble fiber; however, they are generally relatively high in fat and calories. It is generally desirable, for many applications, to have a dietary fiber material with an advantageous ratio of insoluble to soluble fibers, i.e., total dietary fiber to soluble fiber, and a relatively low fat and caloric content.
A wide variety of food sources, such as fruits, grains, and vegetables, and food additives, such as cellulose and gums, supply dietary fiber. For example, wheat bran has approximately 42% to 55% total dietary fiber, of which only about 3% to 6% is soluble fiber. Cellulose, which is used as a food additive for thickening purposes, has a total fiber content of about 92% to 100%, which is mostly insoluble fiber; whereas, gums have approximately 80% to 90% total fiber, which is mostly soluble fiber. Herein, the percentages referred to are weight percentages unless otherwise noted. Herein, the total dietary fiber is based upon the total dry weight of the material, and the soluble fiber content is reported as a percentage of the total dietary fiber content, unless otherwise noted. Alternatively, the soluble fiber content can be reported as a percentage of the total dry weight of the material.
The values for total dietary fiber and soluble fiber components depend, at least in part, upon the material and/or product, e.g., how it was processed and its source, and upon the method used to analyze the product. For example, certain apple fiber products contain about 40% to 60% total dietary fiber, anywhere from about 2% to 30% soluble fiber, depending upon the product, and approximately 1 to 2 calories per gram; whereas, certain dried apple products contain about 11% total dietary fiber, 25% soluble fiber, and 3.6 calories per gram. Wheat germ products contain about 10% to 20% total dietary fiber, anywhere from about 2% to about 88% soluble fiber, and approximately 3 to 7 calories per gram; whereas, wheat bran products contain about 42% to 55% total dietary fiber, about 3% to 6% soluble fiber, and approximately 1 to 2 calories per gram. Corn bran contains anywhere from about 50% to 95% total dietary fiber, less than about 5% soluble fiber, and less than about 1.2 calories per gram. Oat fiber, which is made from oat hulls, contains about 67% to 98% total dietary fiber, about 1% to 7% soluble fiber, and less than about 0.5 calories per gram. Oat bran typically contains about 16% to 24% total dietary fiber, of which about 25% to 50% is soluble fiber. The caloric content of oat bran is generally about 3 to 5 calories per gram with about an 8% fat content. Rice bran, which is the thin brown layer that is removed during the processing of white kernels of rice, contains approximately 20% to 40% total dietary fiber, about 5% to 7% soluble fiber, and approximately 2 to 3 calories per gram, with certain rice products having a fat content of up to about 20%. Barley bran, which is generally produced from barley remaining after a brewing operation, contains anywhere from about 50% to about 70% total dietary fiber, typically about 3% to 4% soluble fiber, and approximately 1 to 2 calories per gram. Certain barley products have been reported to contain up to about 20% soluble fiber. Soy-containing products that contain both bran, which is from the external portion of the soybean, and fiber, which is derived from the internal portion, i.e., cotyledons, generally have about 65% to 70% total dietary fiber, up to about 10% soluble fiber, and about 1 calorie per gram. Soy-containing products without the hulls, i.e., soy fiber, generally contain anywhere from about 45% to 75% total dietary fiber, with some products reported to contain up to about 81%. The range of the soluble component in soy fiber products is anywhere from about 7% to 60% and the caloric content is typically within the range of about 0.5 to 1.5 calories per gram. Cellulose typically contains approximately 0 calories per gram and 92% to 100% total dietary fiber, which is almost totally insoluble fiber; pectin contains about 87% to 100% total dietary fiber, which is mostly soluble fiber; and, gums, such as guar, arabic, locust bean, karaya, agar, and tragacanth, contain approximately 80% to 90% total dietary fiber, which is almost all soluble. See, for example, "Dietary Fiber Guide" in Cereal Foods World 1987, 32, 555; and, "Status Report: FIBER" in Food Processing 1989, 50, 19.
It is noted that in evaluating the data for the fiber percentages reported in the literature, care must be taken to consider the method of analysis used in determining these values. A widely accepted method of analysis for determining fiber content is the AOAC (Association of Official Analytical Chemists) TDF method, sometimes referred to as the "Prosky Method" (AACC Approved Methods, 8th Ed., Method 32-05).
As stated previously, soluble fibers have been shown to reduce serum cholesterol levels and reduce or eliminate insulin dependency for diabetics. Therefore, dietary fiber materials with a relatively high soluble fiber content are desirable; however, as stated above, high concentrations of soluble fiber can present problems in the incorporation of the material into food products. For example, gums, which are almost 100% soluble, are generally not used at a level of more than about 10% of the weight of the food product. This is generally because of the viscosity properties of the materials, which present processing difficulties. That is, the more soluble fiber a material possesses, the more difficult is the food product to process upon its incorporation, because the material has a strong tendency to gel. In other words, the product becomes too "thick" to process, e.g., mix and/or extrude, properly. Insoluble fiber components do not present such processing problems, and are generally easily processed. Thus, a combination of soluble and insoluble fibers is advantageous from a processing perspective. Furthermore, since insoluble fibers are believed to provide additional and different health benefits than do soluble fibers, a dietary fiber material with a combination of insoluble and soluble fiber, wherein the soluble component is not so high as to cause processing problems, is advantageous.
Oat fiber has a combination of soluble and insoluble fiber components, as does corn fiber, soy fiber, and a variety of other fiber-containing materials. Certain of these materials provide advantageous processing results; however, many of these materials contain a relatively low soluble fiber content, such that the health benefits are not necessarily realized at least to a preferred extent, and/or they are relatively high in fat and caloric content. The relatively high fat and caloric contents are not typically desirable features, especially for those consumers who are also in need of reducing their fat and caloric intake. Although often the fat can be removed, this generally requires chemical treatment, which does not always remove all the fat, especially in a product such as oat bran in which the fat is quite diffuse. Therefore, it is desirable to produce a dietary fiber material that is relatively high in total dietary fiber, relatively high in soluble fiber, but not so high as to present processing problems, and relatively low in fat and caloric content naturally, i.e., without further treatment.
Sugarbeet fiber, also referred to as sugarbeet pulp, is the vegetable material remaining after sugar has been extracted from the sugarbeet. The common beet "Beta Vulgaris" is commercially grown in large quantities for sugars and upon its processing, a fiber by-product is generated. Depending upon the species, growing conditions, and other factors, unprocessed mature sugarbeets typically consist of about 80% to 85% water, 10% to 22% sugar, 5% to 8% fibrous material, and minor amounts of other components such as organic acids, amino acids, proteins, lipids, and minerals. The sugar content of sugarbeets is typically extracted by immersing slices, i.e., cossettes, in water under conditions sufficient to cause a transfer of the sugar from the sugarbeet cossettes to the water. The process results in an aqueous solution of sugar commonly referred to as the juice and a mass of water insoluble material commonly referred to as the pulp, or fiber. The sugar is typically extracted from the juice by crystallization and sold as a sweetener, while at least in the past the pulp has been typically dried and treated as a waste or sold as livestock and other animal feed. Use of the pulp has generally been limited to livestock and other animal feed, at least in part, because the pulp has an unappetizing flavor (off-flavor) and unappealing odor or smell (off-odor). These not only make the material generally unacceptable for incorporation into human foods, but they also make processing unpleasant.
The dry sugarbeet fiber material is relatively high in total dietary fiber content, generally above 75% and typically at least about 80%, and contains both soluble and insoluble fibers. In addition to its high total fiber content, it is very low in fat and calories. Typically, sugarbeet fiber contains less than about 1% fat, and less than about 1 calorie per gram. The soluble fiber content generally ranges from about 10% to 25%, of the total fiber content (or about 8% to 23% of the total dry weight of the material), which is high enough to provide beneficial health effects but not so high as to adversely effect the functional properties of the material.
Because of its relatively high total dietary fiber content, its relatively high soluble fiber content, and its relatively low caloric content, sugarbeet fiber offers excellent dietary and physiological benefits to consumers. Furthermore, sugarbeet fiber also offers manufacturing and functional advantages to food processors. It has excellent moisture retention, good texture and mouth feel, excellent expansion and extrusion properties, and can be produced in a variety of particle sizes for relatively easy blending with other ingredients. Sugarbeet fiber has also been of much lower cost than gums and other soluble fibers, and competitive in cost to insoluble fibers. Thus, this material would arguably be desirable for use in such products as cereals, bakery products, pasta, processed meats, soups, and snacks, but for the presence of the off-flavor and off-odor problems.
A small percentage of sugarbeet fiber, even with its undesirable flavor and odor, may be usable in very small quantities in human consumable products, such as selected bakery applications and cereals. This amount, however, would generally be limited to not more than about 2% by weight. As stated previously, the majority of sugarbeet fiber, in the past, has been used in animal feeds, where odor and taste are less of a problem. Thus, in the past sugarbeet fiber has been of very limited commercial value.
Over 20 million tons (1.8.times.10.sup.10 kg) of sugarbeets are harvested every year in the United States, and sugarbeet refining generates approximately 5.5% fiber from the beet. Therefore, the United States sugarbeet industry produces over one million tons (9.0.times.10.sup.8 kg) of sugarbeet fiber annually. Within ten years, it is estimated, at least 50 to 60 million pounds (2.3.times.10; to 2.7.times.10; kg) of this material could be readily utilized in the human consumable marketplace per year, if the odor/taste problems could be overcome.
Many methods have been used to treat sugarbeet pulp in an attempt to render it fit for human consumption. Most of these methods have not, however, effectively and/or satisfactorily eliminated or controlled the off-flavor and off-odor, which may even be enhanced during processing and storage. Other methods are known that have apparently eliminated or controlled the off-flavor and off-odor; however, this has not been done without adding other undesirable components to the sugarbeet pulp and/or without use of undesirable processing methods.
For example, in U.S. Pat. No. 4,379,782 it is disclosed that sugarbeet pulp may be extracted with isopropyl alcohol to remove off-colors and off-flavors. In U.S. Pat. No. 4,451,489 it is further disclosed that sugarbeet pulp can be contacted with an alcoholic solution such as methanol, ethanol, or isopropanol, to remove bitter constituents and colors. Other solvents disclosed as removing bitter constituents and color include t-butyl alcohol, ethylene glycol, monomethyl ether, 2-methylethyl ether, and hexane.
However, it is known that residual amounts of organic solvents, such as alcohol, are extremely difficult to remove from sugarbeet pulp. In some instances vacuum techniques are required. After such a process, the residual alcohol in the pulp can be reduced to less than about 500 ppm. The difficulty with which alcohols, as well as other organic solvents, are removed from sugarbeet fiber could be a result of case hardening of the surface of the sugarbeet fiber during drying resulting in the physical entrapment of the alcohol. Alternatively, it could be a result of the components of sugarbeet fiber chemically "fixing" the alcohol. As a result, an organic solvent-free, e.g., alcohol-free, method is needed to effectively and satisfactorily eliminate or reduce the off-flavor and off-odor of a vegetable fiber material such as sugarbeet fiber. Another reason why it is desirable to avoid organic solvents in processing is to avoid the special precautions required in handling flammable solvents, toxic fumes, and organic waste solutions.